Haruna's chapter is still my favourite from this, it captures the feeling of growing up being the thing everyone warned you to stay away from and tried to hide from you because it's "bad" and how often some will try to deny being so themselves really well.
And really just the entire idea of watching yourself slowly turn into something you never expected to, how unfair it is that you're the one going through it while everyone else seems fine and are never going to be the thing, is very relatable. She was never going to be able to fit in, you can do everything you can to hide from your kids that those things exist, try to beat it out of them, but it'll never cease to exist and it'll only keep coming back.
Then your feelings slowly changing, until they become something "vile" in the eyes of an outsider, when for you it's just something natural that you need to survive. Although it's justified this time for there to be a fear of them because they seem to eat humans, the act of eating humans itself is not evil and Haruna's state at the end was like she was still stuck with things that are harmful for her being (wanting to conform) when the fish mindset is her natural. The fear when those changes started to happen, the loneliness of not being able to tell anyone about it and not being able to do a thing about it... But no matter what, there was no way of keeping the things that made her think she was safe (even if it was the sort of safety that comes from knowing what will happen) from being destroyed, even if she tried to hide it and control her instincts, she would have starved to death for the sake of others that wouldn't ever dare to give her the same amount of thought.
Even if this was caused by someone else, that's still punishing what could be seen as a victim.
Yeah puberty ruined my life